On the specific status of eastern Mediterranean Dendrophyllia corals (Cnidaria, Anthozoa): Genetic characterization and speciation scenarios

Abstract

The deep‐sea corals Dendrophyllia ramea and Dendrophyllia cornigera occur in Mediterranean and Atlantic waters. Both species are found in different environmental conditions, and they can colonize hard and soft substrates. These species then display an important ecological plasticity along with morphological plasticity. Nevertheless, there is a large knowledge gap on the genetic characteristics of the two species, including on the relationships between them and the possibility of cryptic species along their range. The recent discovery of Dendrophyllia populations off Cyprus in the eastern Mediterranean Sea raised new questions in this context. These corals were related to D. ramea but had some morphological differences with other known populations of this species. Here, we study the specific status of Dendrophyllia corals from Cyprus on the basis of morphology and genetics. The genetic data are interpreted by comparison with the same analysis performed on two Caryophyllia species. Both morphological and genetic data confirm that corals found off Cyprus belong to the D. ramea species. We further tested the speciation scenario using transcriptome data: the results indicate an absence of current gene flow between D. ramea and D. cornigera and that the divergence occurred more than 3 million years ago. We discuss the possible historical and ecological factors which may have shaped speciation in these species.

Symbiotic status does not preclude hybridisation in Mediterranean octocorals

“…If we suppose a lower hypothesis of generation time of two years for Eunicella species, with a median estimate of divergence time around 900 000 generations for E. verrucosa / E. singularis and 1 000 000 for E. verrucosa / E. cavolini, and based on a mutation rate set at 3.10 -9 , this would indicate a divergence at least around 2 000 000 years (2 Ma). As a comparison, this is of the same order as estimates of divergence time for sister scleractinian species which can go from around 1 Ma to 4-5 Ma (Aurelle et al, 2024;Johnston et al, 2017). Note that higher generation time would point to divergence time older than 5 Ma, where the Messinian crisis (between 5.5 and 6 Ma; Rouchy & Caruso, 2006) could have played a role in initiating divergence.…”